Process for drawing sheet glass



Nov.vk 15,1933. 7 j2,137,12o

` f Y i fREss FORDRAWINYQ SHEET GLASS Filed Deo. l2, 195e Y .f f2Y sheets-sheet 1 y//v VEN To@ y nfroe/ya'y.

`Patented Nov..15, `19381 j UNIT-EDsrrfs Y -almzo. PROCESS roRpRAwrGsnEErcLAss James Bonar WattfSt.' Helens, England, lassignor` Y trPittsbui-gh Plate Glass Company, Pittsburgh,

wPa., a companyofI Pennsylvania Y -Applicatinnecmber 12,1936,se'ri`a1`N0.115,547 InfGreatfBi-itain December 18, 1935 f i ironing wma-83,15 ,i

Y lThis invention relates togapro'cess for drawing flat glass in wlri-ch,the width of .the shefetzis maintained by rollers, as in the Colburn type `of apparatus, and 'hasfor its objectanimprovement 5 therein whereby the` glass in the neighbourhood of 'the' edges'is "of more uniformv thickness:

4In drawing sheet glass in the type of appa- )ratus .-mentioned, lit Ais customary" to;r bend' the drawn strip over a roller andanneal'itiin a horilo zontal lehr. The action of the widthf'maintaining rollers, however, produces variations `in thick-` ness in the neighbourhoodofthe edges suclrthat c it cannot be annealediwithdut lrisklof"breakage in an ordinary vertical towerv of the` type used in `l thev Fourcault process. i

According to the invention, laV pair ofy members located below the rllersfateach edge; engagev the glass rising fromthe bathso-asto' determine the thickness of the glass mass reachingthe rollers.

11120 The pair' of members' are preferably "the fpr'on'gs of a fork located so that the edge :portion ofthe rising glass passes between them. Preferably meansare providedfor adjusting the effective width of the space between the two members of each pair, to control the thickness of the glass reaching the rollers;

In the accompanying drawings, Figure 1 is a central vertical section of a drawing apparatus, in which details are omitted.v Fig. 2 is a section through one edge of the sheet produced, Fig. 3

is a diagrammatic vertical sectionat the base l of the glass sheet, such section `b'eingytaken through the width-maintaining rollers `and the edge retarding members.- Fig. l` is a central ver- 35 tical section showing the operative ends of `one roller and the said member. Fig. 5 is a plan view of the same. Fig. Gis a section similar to that of Fig. 4 on a reduced scale showing further parts of the apparatus. Fig. 7 is a section similar to l that of Fig. 6` showing anv alternative form of member.,Fig..S is -arr end view thereof. And Fig. 9 is a plan view of the members.l

Referring to Fig. 1, the sheet-I is drawn from thef'bath of molten glass 2 contained in the -forehearth of the furnace. The width of the sheet is maintained by rollers 4. The rollers 5 arev the v first rollers drawing the strip upwards `into a.v

vertical annealing tower. The members which form'the subject ofthe invention arerepresented by the parts 6. The remaining portions of the ligure represent a drawing apparatus 'of ordinary l type and thereforeneed not be further described. In order to understand the result secured by w the use of the parts 6, 6 in conjunction with the edge maintainingrolls 4, 4 of the prior art,`itis necessary to consider the edge conditions' pro- `duced when edge-@maintaining rollers are used alone and when fixed members, such as the parts 6, 6 'are'used alone. Either ofsuch edge holdingmeans will prevent'the sheetedges from 5 working away froxn the sides' of the tank, and

f thus `narrowing the sheet asV the drawing` progresses, but have` certain drawbacks which vare avoided whentheu edge' rollers arel used in come bination with the members 6; 6 as` heretofore 10 later set forth.`l When the edge rollers areused alone, a thinning ofthe sheet occursfinward from-fthethickened portion 1.(engaged 'by the frollerslthepoint of'thinning being locatedin- -jward a substantialdistance from `the thickened `15k portion atn lap'p'oximately. the point indicated by Ythenugmeral- `8 'o n Fig. 2. Depending on the lengthof th'e'rollers'll, 4' and their` distance apart,

the edge produced may val'sohave' aportionfof greater thickness thanthefportionl lying be- :20 j

tweensuch portion and thev thin point above referred to. n These conditions of thick and'thin produced by the actionA of. the edge rollers, when `used alone, tend to cause breakage during the drawing operation, and require that a wider edge 25 be trimmed from thenished sheet than would otherwiserbe the case. When, on theother hand, the edge rollers aredispensed with, and a holding fork, such as the members 6, 6 is used alone to hold the sheet edge, it is diiicult toy secure an 30 edge which is not too hard and therefore subject to vents and breakage, and there is a tendency to produce 'very slight, butoptically apparent diagonal waves in the sheet drawn.

The use of the pair of members 6, 6 in conjunc- 35 @tionwith the edge rollersv avoids the 'foregoing .di'iculties The sheet produced has an extreme edge of the thickness determined by the spacing of the rollers 4, 4 preferably slightly thicker than the'mainbody of the sheet, as indicated in Fig. 2, 40 and Vthereis no appreciable thinning of the sheet at 8,` which, as above pointed out, ,occurs when the rollers are used alone. The tendency to breakage incident -to thick and thin is thus avoided and' wastage,"incid`ent to trimming, is 45`v 6, engage the glass. risingl up to the rollers holding rolls are used alone.

A sheet with the edge as shown in Fig. L2,

can be annealed in an ordinary vertical tower of theFourcault type. The permissiblevariations in the thickness at the edge of the sheet depend on the conditions of drawing and an.- nealing and can be ascertainedr for any'given set of conditions only by trial. For this purpose;

` the form of the edge may be varied by varying at I5, carried on the support I6.

the width apart or the positionof the pair of members 6, G as hereinafter described.

Figs. 4, and 6 show one constructional form -of the invention. The rolls 4 are on the shafts i4 running in` bearings, of which one is shown The rollers are adjustable in respect'to .their distance apart and are water or air cooled through the shafts `|4. Since the rollers are ofwell known form,

their constructional details are vomitted from the drawings. yThe members 6 are, in this form, the prongs of a fork l1, which passes up between the shafts I4 and is supported on the support I6 by bolts I8. l

' In an alternative constructional form shown in'Figures 7', 8 and 9 the members 6 areeach attached to a lug I9 depending from a bar 20.

The two bars 20 are xed to brackets` 2l, carried -Von the support` I6, by bolts 22, with intermediate distance piece 23.- Beyond the distance piece 23, the bars 20 are spaced apart and their spacing canv'be adjusted by means of the bolt and nut 24. By ,adjusting theboltl andnut 2 4, the distance apart of the two members (if can be adjusted.

An equivalent adjustment can be effected by the simpler construction of Figures 4, 5 and 6. In this, the two members i are formed, as at 25, to give a tapering space between them, and the bolts I8 by which the fork I1 is held to the support I0 pass through a slot 26in the fork. Bythis means, the fork I1 can be adjusted endwise and, thereby, the average width of the space between the members 6, immediately unkvder the rollers 4 'can be varied. This construction, therefore, affords a means for adjusting the effective width of the space between the members, andit also enables, by means of the bolts i8, the height of the members 6 to be adjusted.

*By 'determining the thickness of the glass reaching the rollers, in accordance with the invention`,vglass is produced having less stress in theneighborhood of the edges. The width of glass which has to be cut to waste oi the edges is less, and `the operation of drawing is more stable and lessvaiflected by temperature varia tions. .l

lThe invention may be applied to drawing apparatus employing width-maintaining4 rollers, with various `forms ofv accessory devices such,

for instance, as theV bar, 21 (Figure 1) for locating the line of draw in'the bathof glass.

Having described my invention, I declare that what I claim and desire to secure by Letters Patent isz- A process of making aglass sheet which consists in drawing it vertically from a bath, thinning the edge of the sheetr by dragging it without chilling through a retarding` fork whose glass engaging portions are stationaryand located so `as to engage the edge of the tapering meniscus of the sheet, but. entirely above the bath, and applyingrolling ltraction tov the sides of the sheet edge just above said fork at a level at which the edge is stlllplastic, so as to further` JAMES BONAR WA'II.` Y 

